There is a widely felt need for an improved or "ideal" cardioplegic solution, literally paralysing the heart (to stop electrical and mechanical activity) for prolonged and safe preservation of the myocardium (heart muscle). Such solutions are perfused through the vessels and chambers of the organ and, while maintaining viability, cause its intrinsic beating to cease. The effects of such solutions should be totally reversible, so that the heart resumes substantially normal functional activity once the cardioplegic solution has been replaced by blood. The provision of cardioplegic solutions is highly desirable during the procurement, transportation and storage of donor hearts for use in the increasingly frequently performed heart transplantation procedure and is even more desirable during open-heart surgery. Myocardial revascularisation (coronary artery surgery) and repairs (aortic and mitral valves replacement) is best achieved with a motionless and bloodless heart.
After cardio-pulmonary bypass is initiated the heart is infused with a cardioplegic solution. The presently available clinical cardioplegic solutions are considered to be imperfect as they provide reversible myocardial protection after hypothermic cardioplegic "arrest" for only a short period (up to 5 hours at 4.degree. C. or less than 3 hours at 15.degree.-20.degree. C.). Even during that period the heart sustains some degree of ischemic injury which becomes progressively worse with time, resulting in significant deterioration of myocardial function on reperfusion which exacerbates the problems of post-operative recovery. The heart does not regain the efficiency it had before the bypassing procedure.